1. Field of the Invention
The present invention relates to a light emitting device and an apparatus using the light emitting device, and more particularly, to a light emitting device and a light emitting apparatus using an LED (light-emitting diode) chip or the like, and an apparatus such as a luminaire, a display unit or the like, which uses the light emitting device.
2. Description of the Background Art
As a small-type light emitting device, a cannonball-shaped LED in which an LED chip is sealed in a transparent mold resin is well known. According to the light emitting device, although the light emitted from the LED chip forward passes through an interface of the mold resin and directly emitted from the light emitting device, the light emitted from the LED chip in the slanted direction is totally reflected by the interface of the mold resin or scattered in its case, which becomes loss and lowers light usability. In addition, it is difficult to increase an area in such light emitting device.
Therefore, there has been conventionally proposed a thin and large light emitting device in which light emitted from an LED chip in the slanted direction can be also effectively emitted forward. FIG. 1 is a perspective view showing a structure of such light emitting device 1, FIG. 2A is a sectional view thereof and FIG. 2B is a graph showing distribution of its front face luminance. That light emitting device is disclosed in Japanese Unexamined Patent Publication No. 2002-94129 (patent document 1). According to the light emitting device 1, an LED chip 3 is sealed at a center in a transparent mold resin 2 which is in the shape of almost a dish, and a reflection mirror 4 in the shape of a concave mirror is provided on a back face of the mold resin 2. In addition, a direct emitting portion 5 in the shape of a convex lens is formed at a center of a front face of the mold resin 2, and a planar ring-shaped total reflecting portion 6 is formed around it.
Thus, when the LED chip 3 is energized and emits light, as shown in FIG. 2A, the light L emitted from the LED chip 3 toward the direct emitting portion 5 is refracted by a lens function when it passes through the direct emitting portion 5 in the shape of the convex lens, and emitted from the light emitting device 1 almost straight forward. In addition, the light L emitted from the LED chip 3 to the total reflecting portion 6 is totally reflected by the interface of the total reflecting portion 6, reflected by the reflection mirror 4, passes through the total reflecting portion 6 and emitted from the light emitting device 1 almost straight forward.
According to the light emitting device 1, the light L totally reflected by an inner periphery part of the total reflecting portion 6 is directed to the reflection mirror 4, reflected by the reflection mirror 4, reaches the total reflecting portion 6 again and then, emitted from the total reflecting portion 6. Thus, while the light L is directed from the total reflecting portion 6 to the reflection mirror 4, the light spreads to the outside of the inner peripheral part of the total reflecting portion 6, so that the light is emitted from the outer peripheral part of the total reflecting portion 6. Therefore, as shown in FIG. 2A, although the direct emitting portion 5 and the outer peripheral part of the total reflecting portion 6 are light emitting regions, light is not emitted from the inner peripheral part of the total reflecting portion 6 positioned between them and the inner peripheral part is a region where light is not emitted.
FIG. 2B is a graph schematically showing luminance distribution when viewed from the front face of the light emitting device 1, in a section through which a central axis of the light emitting device 1 passes, and FIG. 3 is a front view showing the light emitting device. As shown in FIGS. 2A and 2B, there is a region where the light is not emitted in the light emitting device 1. Thus, according to the conventional light emitting device 1, since a ring-shaped dark part (dark ring) having a wide width is generated when viewed from the front face, light cannot be uniformly emitted on the plane. Especially, when the light emitting device has a diameter of several centimeters, this dark part is very clearly seen and uniform planer light emission cannot be implemented.
In addition, Although Japanese Unexamined Patent Publication No. 2002-134794 (patent document 2) discloses a method of reducing the dark part by providing a ling-shaped reflection plate or a slit (air layer) at an outer peripheral part of the direct emitting portion, in this light emitting device, molding process of the mold part becomes complicated and after-process is necessary, which increases the cost.